A rifle shoots a $10 \mathrm{~g}$ bullet with an average force of $900 \mathrm{~N}$ which acts during a fraction of a second. Compare the acceleration of the bullet to the acceleration of the system composed by the rifle and the shooter, which have a combined mass of $80 \mathrm{~kg}$.
$$
\left[9.0 \cdot 10^{4} \mathrm{~m} / \mathrm{s}^{2} ; 11 \mathrm{~m} / \mathrm{s}^{2}\right]
$$